Wireless communication device, wireless communication system, and transmission terminal

Abstract

A wireless communication device (200) comprises a wireless communication unit (210) wirelessly communicating with a plurality of transmitting terminals (100), and a processor (220) connected to the wireless communication unit (210). The processor (220) executes processing of: determining whether or not a conflict occurs among wireless resources reserved for use by the plurality of transmitting terminals (100) for data transmission; if a conflict of wireless resources is determined to occur, determining the presence or absence of reselection of a wireless resource by the transmission terminal (100); generating a reselection request according to the determined presence or absence of reselection; and causing the wireless communication unit (210) to transmit the generated reselection request.

Description

Technical Field

[0001] The present invention relates to a wireless communication device, a wireless communication system, and a communication control method.

Background Art

[0002] In the current network, the traffic of mobile terminals (smartphones and feature phones) occupies most of the network resources. Also, the traffic used by mobile terminals tends to increase in the future.

[0003] On the other hand, in line with the deployment of IoT (Internet of Things) services (such as traffic systems, smart meters, and device monitoring systems, etc.), it is required to support services with various requirements. Therefore, in the communication standard of the fifth-generation mobile communication (5G or NR (New Radio)), in addition to the standard technology of 4G (the fourth-generation mobile communication), technologies for achieving further higher data rates, larger capacities, and lower latencies are required.

[0004] In order to support a wide variety of services, 5G assumes the support of many use cases classified into eMBB (Enhanced Mobile Broad Band), Massive MTC (Machine Type Communications), and URLLC (Ultra-Reliable and Low Latency Communication).

[0005] In addition, in the working group of 3GPP, discussions are also being held on NR-V2X (New Radio Vehicle to Everything) communication. NR-V2X is a general term for, for example, V2V (Vehicle to Vehicle) for vehicle-to-vehicle communication, V2P (Vehicle to Pedestrian) for communication between vehicles and pedestrians, V2I (Vehicle to Infrastructure) for communication between vehicles and road infrastructure such as signs, and V2N (Vehicle to Network) for communication between vehicles and the network, etc., using sidelink channels.

[0006] Regarding the allocation of radio resources (hereinafter simply referred to as "resources") in NR-V2X, it is considered to provide a control channel (PSCCH: Physical Sidelink Control CHannel) and a data channel (PSSCH: Physical Sidelink Shared CHannel). SCI (Sidelink Control Information) including information such as the modulation method and coding rate of the data of the corresponding PSSCH is mapped to the resources of the PSCCH.

[0007] When mode 2 of NR-V2X in which the terminal device autonomously selects the resources used for data transmission is executed, the SCI is also used to notify the resources reserved by the terminal device. That is, when the terminal device that transmits data selects the resources used for data transmission, it maps the SCI for reserving this resource to the PSCCH and transmits it. Therefore, other terminal devices receive the SCI to grasp the reserved resources, and when they transmit data themselves, they exclude the reserved resources and select the resources they use for data transmission.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

[0009] [Non-Patent Document 1] Ericsson, "Mode 2 enhancements using Inter-UE coordination", 3GPP TSG RAN WG1 #104b-e, R1-2103705, April 12th-20th, 2021 [Summary of the Invention] [Problems to be Solved by the Invention]

[0010] By the way, when a plurality of terminal devices each autonomously select resources, depending on the timing at which each terminal device transmits an SCI, collisions of reserved resources of the plurality of terminal devices may occur. Specifically, for example, when two terminal devices select overlapping resources almost simultaneously and transmit an SCI notifying the reserved resources, collisions of the reserved resources of these two terminal devices occur.

[0011] Therefore, when a terminal device that receives SCIs from these two terminal devices detects a collision of reserved resources, it is considered to avoid the collision of reserved resources by requesting the terminal device that is the transmission source of the SCI to reselect resources. In this way, by a terminal device that cooperates with a terminal device that transmits data avoiding a collision of reserved resources, the communication efficiency of the entire system can be improved.

[0012] However, in an environment where resources are congested, for example, there is a problem that collisions of reserved resources are frequently detected, a large number of re-selections of resources occur, and collision avoidance may not function sufficiently. That is, for example, when a large number of terminal devices share resources and execute NR-V2X in mode 2, collisions of reserved resources frequently occur, and many terminal devices are required to re-select resources. As a result, there is a high possibility that re-collisions occur where the re-selected resources overlap with the reserved resources of other terminal devices, and sufficient improvement in communication efficiency cannot be achieved.

[0013] In addition, when a plurality of terminal devices detect a collision of reserved resources, these terminal devices may each request a re-selection of resources for different terminal devices, and unnecessary re-selection of resources may occur. That is, for example, when a collision occurs between the reserved resources of two terminal devices, a plurality of terminal devices may cooperate with these two terminal devices, and both of the two terminal devices may be required to re-select resources. Also in such a case, as a result of the resources being re-selected unnecessarily, there is a possibility of re-collision with the reserved resources of other terminal devices, and sufficient improvement in communication efficiency cannot be achieved.

[0014] The disclosed technology has been made in view of such points, and an object thereof is to provide a wireless communication device, a wireless communication system, and a communication control method capable of improving communication efficiency.

Means for Solving the Problem

[0015] The wireless communication device disclosed in the present application, in one aspect, includes a wireless communication unit that wirelessly communicates with a plurality of transmission terminals, and a processor connected to the wireless communication unit. The processor determines whether a collision occurs in wireless resources reserved for use by the plurality of transmission terminals for data transmission, and when it is determined that a collision of wireless resources occurs, determines whether there is a re-selection of wireless resources by the transmission terminals, generates a re-selection request according to the determined presence or absence of re-selection, and executes a process of causing the wireless communication unit to transmit the generated re-selection request.

Effect of the Invention

[0016] According to one aspect of the wireless communication device, wireless communication system, and communication control method disclosed in the present application, there is an effect that communication efficiency can be improved.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0018] Hereinafter, embodiments of the wireless communication device, wireless communication system, and communication control method disclosed in the present application will be described in detail with reference to the drawings. Note that the present invention is not limited by this embodiment.

[0019] (Embodiment 1) FIG. 1 is a diagram showing a specific example of a wireless communication system according to Embodiment 1. As shown in FIG. 1, for example, a plurality of terminal devices mounted on an automobile each form a group with other terminal devices located within their communication range (Communication Range) CR from their own devices, and execute group casting within the group. That is, the terminal devices each transmit a signal to other terminal devices within their respective communication ranges CR and receive a signal from other terminal devices within their respective communication ranges CR. Further, the terminal devices may establish a unicast link with a specific terminal device and execute unicast for one-to-one communication via the unicast link. Furthermore, the terminal devices may execute a broadcast without specifying the destination terminal device.

[0020] In FIG. 1, transmission terminals Tx#1, #2 that transmit signals, reception terminals Rx#1 to #4 that receive signals, and a coordinative terminal Co that receives signals and cooperates with the transmission terminals Tx#1, #2 are illustrated. Note that since the transmission terminals Tx#1, #2, the reception terminals Rx#1 to #4, and the adjustment terminal Co are all equivalent terminal devices, the transmission terminals Tx#1, #2 can also be reception terminals that receive signals from other terminal devices, and the reception terminals Rx#1 to #4 and the adjustment terminal Co can also be transmission terminals that transmit signals to other terminal devices. Also, all terminal devices other than the transmission terminals Tx#1, #2 may be coordinative terminals.

[0021] When data to be transmitted is generated, the transmission terminals Tx#1, #2 select a resource to be used for data transmission based on the SCI already received from other terminal devices. That is, the transmission terminals Tx#1, #2 identify the resources (reserved resources) reserved by other terminal devices from the SCI already received from other terminal devices, and select resources in a region where the reserved resources do not overlap in terms of time and frequency. Then, the transmission terminals Tx#1, #2 generate an SCI that notifies the selected resources as the reserved resources of their own terminals and transmit it to the terminal devices within the group. Then, the transmission terminals Tx#1, #2 transmit data using the selected reserved resources.

[0022] Also, when the transmitting terminals Tx#1 and #2 receive a resource reselection request from the cooperating terminal Co, they select a resource that does not overlap with the reserved resources of other terminal devices and is different from the previously selected reserved resource. Since the transmitting terminals Tx#1 and #2 receive a reselection request from the cooperating terminal Co when a collision occurs between the reserved resources selected by their own terminals and the reserved resources of other terminal devices, they reselect their own reserved resources.

[0023] The receiving terminals Rx#1 to #4 receive the SCI transmitted from the transmitting terminals Tx#1 and #2 and identify the reserved resources of the transmitting terminals Tx#1 and #2. Then, the receiving terminals Rx#1 to #4 receive the signals transmitted from the transmitting terminals Tx#1 and #2 in their respective reserved resources and decode the received signals. The receiving terminals Rx#1 to #4 may feedback feedback information such as ACK or NACK to the transmitting terminals Tx#1 and Tx#2 according to whether the decoding of the received signal is successful.

[0024] The cooperating terminal Co receives the SCI transmitted from the transmitting terminals Tx#1 and #2 and identifies the reserved resources of the transmitting terminals Tx#1 and #2. Then, the cooperating terminal Co determines whether a collision occurs in the reserved resources of the transmitting terminals Tx#1 and #2, and if a collision occurs in the reserved resources, determines whether the transmitting terminals Tx#1 and #2 should reselect resources. Specifically, the cooperating terminal Co calculates, for example, the risk of data error (hereinafter referred to as "error risk") when the transmitting terminals Tx#1 and #2 transmit data using the reserved resources from the ratio of the overlapping area of the colliding reserved resources. Then, when the error risk is equal to or greater than a predetermined threshold, the cooperating terminal Co decides to let the transmitting terminal Tx#1 or the transmitting terminal Tx#2 reselect resources and requests resource reselection. The configuration and operation of the cooperating terminal Co will be described in detail later.

[0025] FIG. 2 is a block diagram showing the configuration of the transmission terminal 100 according to Embodiment 1. The transmission terminal 100 shown in FIG. 2 corresponds to the transmission terminals Tx#1 and #2 shown in FIG. 1. As shown in FIG. 2, the transmission terminal 100 includes a processor 110, a memory 120, and a wireless communication unit 130.

[0026] The processor 110 includes, for example, a CPU (Central Processing Unit), an FPGA (Field Programmable Gate Array), or a DSP (Digital Signal Processor), and overall controls the entire transmission terminal 100. Specifically, the processor 110 includes a reception control unit 111, a resource selection unit 112, a transmission data generation unit 113, a control information generation unit 114, and a transmission control unit 115.

[0027] The reception control unit 111 demodulates and decodes the reception signal in the wireless communication unit 130, obtains control information such as SCI from a control channel such as PSCCH, and obtains data from a data channel such as PSSCH. At this time, the reception control unit 111 specifies the reserved resources used by other terminal devices as data channels based on the decoding result of the SCI. Then, the reception control unit 111 executes demodulation and decoding of the data channels of other terminal devices to obtain data. Further, when the reception control unit 111 receives a resource reselection request from a cooperating terminal, it notifies the resource selection unit 112 to that effect.

[0028] The resource selection unit 112 selects the resources used by the transmission terminal 100 to transmit data based on the reserved resources of other terminal devices specified by the reception control unit 111. Specifically, the resource selection unit 112 selects, as the reserved resources of the transmission terminal 100, resources that do not overlap with the reserved resources of other terminal devices. The resource selection unit 112 notifies the selected reserved resources to the control information generation unit 114 and the transmission control unit 115.

[0029] Also, when the resource selection unit 112 receives a resource reselection request from the reception control unit 111, it executes reselection of the reserved resource. That is, the resource selection unit 112 reselects a resource that does not overlap with the reserved resources of other terminal devices and is different from the previously selected reserved resource. The resource selection unit 112 notifies the control information generation unit 114 and the transmission control unit 115 of the reselected reserved resource.

[0030] The transmission data generation unit 113 generates data to be transmitted to other terminal devices. The transmission data generation unit 113 generates data to be transmitted by any of unicast, group cast, and broadcast.

[0031] The control information generation unit 114 generates control information regarding the data to be transmitted to other terminal devices. Specifically, the control information generation unit 114 generates an SCI including information specifying the reserved resource selected by the resource selection unit 112. Also, the control information generation unit 114 generates an SCI including information such as the MCS (Modulation and Coding Scheme) of the transmission data.

[0032] The transmission control unit 115 causes the wireless communication unit 130 to transmit an SCI including information specifying the reserved resource using a predetermined control channel. Also, the transmission control unit 115 causes the wireless communication unit 130 to transmit the transmission data using the reserved resource selected by the resource selection unit 112.

[0033] The memory 120 includes, for example, a RAM (Random Access Memory) or a ROM (Read Only Memory), and stores information used for processing by the processor 110.

[0034] The wireless communication unit 130 performs wireless communication with other terminal devices. That is, the wireless communication unit 130 performs predetermined wireless transmission processing on the transmission signal output from the processor 110 and transmits it to other terminal devices via the antenna. Further, the wireless communication unit 130 receives a signal from other terminal devices via the antenna, performs predetermined wireless reception processing on the received signal, and outputs the received signal to the processor 110.

[0035] FIG. 3 is a block diagram showing the configuration of the cooperative terminal 200 according to Embodiment 1. The cooperative terminal 200 shown in FIG. 3 corresponds to the cooperative terminal Co shown in FIG. 1. As shown in FIG. 3, the cooperative terminal 200 includes a wireless communication unit 210, a processor 220, and a memory 230.

[0036] The wireless communication unit 210 performs wireless communication with other terminal devices. That is, the wireless communication unit 210 receives a signal from the transmission terminal 100 via the antenna, performs predetermined wireless reception processing on the received signal, and outputs the received signal to the processor 220. Further, the wireless communication unit 210 performs predetermined wireless transmission processing on the transmission signal output from the processor 220 and transmits it to other terminal devices via the antenna.

[0037] The processor 220 includes, for example, a CPU, an FPGA, or a DSP, and comprehensively controls the entire cooperative terminal 200. Specifically, the processor 220 includes a reception control unit 221, a collision determination unit 222, an error risk calculation unit 223, a reselection request generation unit 224, a transmission data generation unit 225, a control information generation unit 226, and a transmission control unit 227.

[0038] The reception control unit 221 demodulates and decodes the received signal in the wireless communication unit 210, obtains control information such as SCI from a control channel such as PSCCH, and obtains data from a data channel such as PSSCH. At this time, the reception control unit 221 specifies the reserved resource used by the transmission terminal 100 as a data channel based on the decoding result of the SCI. Then, the reception control unit 221 performs demodulation and decoding of the data channel of the transmission terminal 100 to obtain data.

[0039] Based on the SCI acquired by the reception control unit 221, the collision determination unit 222 determines whether a collision occurs in the reserved resources of a plurality of transmission terminals 100. Specifically, the collision determination unit 222 determines whether the time and frequency of the reserved resources of the plurality of transmission terminals 100 overlap from the SCI including information specifying the reserved resources of the transmission terminal 100. When the time and frequency of the reserved resources of the plurality of transmission terminals 100 overlap, the collision determination unit 222 determines that a collision of the reserved resources occurs.

[0040] When it is determined by the collision determination unit 222 that a collision of reserved resources occurs, the error risk calculation unit 223 calculates the error risk of data transmission using the colliding reserved resources. That is, when a plurality of transmission terminals 100 transmit data using overlapping reserved resources, the error risk calculation unit 223 calculates the error risk that an error occurs in the transmitted data. Specifically, the error risk calculation unit 223 calculates the overlap rate of the reserved resources calculated by, for example, the following formula (1) as the error risk. Overlap rate = Overlapping area / Min{Occupied area for each transmission terminal} ···(1)

[0041] However, in formula (1), Min{A} represents the minimum value of set A. Therefore, the overlap rate is the ratio of the area overlapping with the reserved resources of other transmission terminals 100 in the reserved resources of the transmission terminal 100 with the smallest occupied area of the reserved resources. Note that the error risk calculation unit 223 may calculate the overlap rate for each transmission terminal 100 as the error risk for each transmission terminal 100 by, for example, the following formula (2). Overlap rate = Overlapping area / Occupied area for each transmission terminal ···(2)

[0042] In the above formula (1), the error risk for each overlapping area of the reserved resources is calculated, while in the above formula (2), the error risk for each transmitting terminal 100 is calculated. When the ratio of the overlapping area in the reserved resources is large, since the data transmitted using the reserved resources is likely to be in error, the duplication rates in the above formulas (1) and (2) can be used as the error risk of the data. Further, the error risk calculation unit 223 may calculate the error risk by taking into account the MCS information for each transmitting terminal 100 in the duplication rates of the above formulas (1) and (2). In short, the error risk calculation unit 223 calculates the error risk indicating the possibility that the data is in error due to being transmitted using the colliding reserved resources.

[0043] Then, the error risk calculation unit 223 compares the calculated error risk with a predetermined threshold value, and determines whether or not to reselect the resources by the transmitting terminal 100 where the reserved resources collide. That is, when the error risk is equal to or greater than the predetermined threshold value, the error risk calculation unit 223 determines to cause the transmitting terminal 100 to reselect the resources. At this time, when the error risk calculation unit 223 calculates the error risk for each overlapping area as in the above formula (1), for example, it may be determined to cause the transmitting terminal 100 with the smallest occupied area of the reserved resources to reselect the resources. Further, when the error risk calculation unit 223 calculates the error risk for each transmitting terminal as in the above formula (2), for example, it may be determined to cause the transmitting terminal 100 with an error risk equal to or greater than the predetermined threshold value to reselect the resources.

[0044] When it is determined by the error risk calculation unit 223 that the transmitting terminal 100 is to reselect the resources, the reselection request generation unit 224 generates a reselection request for requesting the reselection of the resources. The reselection request generation unit 224 generates a reselection request addressed to the transmitting terminal 100 determined by the error risk calculation unit 223 to reselect the resources.

[0045] The transmission data generation unit 225 generates data to be transmitted to other terminal devices. That is, when the cooperative terminal 200 serves as a transmission terminal, the transmission data generation unit 225 generates data to be transmitted by any of unicast, group cast, and broadcast.

[0046] The control information generation unit 226 generates control information regarding data to be transmitted to other terminal devices. That is, when the cooperative terminal 200 serves as a transmission terminal, the control information generation unit 226 generates control information such as SCI.

[0047] The transmission control unit 227 causes the radio communication unit 210 to transmit the reselection request generated by the reselection request generation unit 224 to the transmission terminal 100 using, for example, a PSFCH (Physical Sidelink Feedback CHannel) for feedback such as ACK or NACK. Further, when the cooperative terminal 200 serves as a transmission terminal, the transmission control unit 227 causes the radio communication unit 210 to transmit the transmission data and the control information.

[0048] The memory 230 includes, for example, a RAM or a ROM, and stores information used for processing by the processor 220.

[0049] Next, a communication control method by the cooperative terminal 200 configured as described above will be described with reference to the flowchart shown in FIG. 4.

[0050] When the SCI including information for specifying each reservation resource is received from a plurality of transmission terminals 100 by the wireless communication unit 210 and the reception control unit 221 (step S101), the reservation resources of each transmission terminal 100 are notified to the collision determination unit 222. Then, the collision determination unit 222 determines whether or not a collision of the reservation resources for each transmission terminal 100 occurs (step S102). Specifically, it is determined whether or not the times and frequencies of the reservation resources of the plurality of transmission terminals 100 overlap. As a result of this determination, if the times and frequencies of the reservation resources do not overlap and no collision occurs (step S102 No), re-selection of resources by the transmission terminal 100 is not necessary, and thus the process ends.

[0051] On the other hand, if the times and frequencies of the reservation resources overlap and a collision occurs (step S102 Yes), the error risk calculation unit 223 calculates the error risk regarding the colliding reservation resources (step S103). Specifically, for example, the overlap rate of the reservation resources shown in the above equations (1) and (2) is calculated as the error risk. Then, the error risk calculation unit 223 determines whether or not the calculated error risk is equal to or greater than a predetermined threshold value (step S104). As a result of this determination, if the error risk is less than the predetermined threshold value (step S104 No), it is determined that re-selection of resources is not necessary because the error risk is low even if a collision of the reservation resources occurs, and the process ends.

[0052] On the other hand, when the error risk is equal to or higher than a predetermined threshold (step S104 Yes), since there is a high possibility that data will be incorrect due to a collision of reserved resources, it is determined that re-selection of resources is necessary. Therefore, a re-selection request for requesting re-selection of resources is generated by the re-selection request generation unit 224, and the re-selection request is transmitted to the transmission terminal 100 by the transmission control unit 227 and the wireless communication unit 210 (step S105). The re-selection request is transmitted to the transmission terminal 100 with the smallest reserved resources or the transmission terminal 100 with an error risk equal to or higher than a predetermined threshold among the plurality of transmission terminals 100 where the reserved resources collide. Note that the transmission destination of the re-selection request may be determined so that the error risk becomes less than a predetermined threshold by re-selection of resources.

[0053] In this way, when a collision of reserved resources of a plurality of transmission terminals 100 occurs, the cooperation terminal 200 calculates the error risk, determines whether to re-select resources by the transmission terminal 100, and when the error risk is high, transmits a resource re-selection request to the transmission terminal 100. Thereby, unnecessary re-selection of resources can be suppressed, and the possibility of re-collision of reserved resources due to re-selection can be reduced. As a result, the communication efficiency in the wireless communication system can be improved.

[0054] Next, the resource re-selection process will be specifically described with reference to the sequence diagram shown in FIG. 5 while giving an example. In the following, the case where the reserved resources selected by the transmission terminals Tx#1 and #2 collide will be described. In FIG. 5, the transmission terminals Tx#1 and #2 are respectively denoted as Tx-UE#1 and Tx-UE#2, and the cooperation terminal Co is denoted as Co-UE.

[0055] The transmitting terminals Tx#1 and Tx#2 select reserved resources for the device to use for data transmission based on the SCI already received from other terminal devices. That is, the transmitting terminals Tx#1 and Tx#2 select, as the reserved resources for their own devices, resources whose time or frequency does not overlap with the reserved resources of other terminal devices. Here, for example, when the transmitting terminals Tx#1 and Tx#2 select reserved resources almost simultaneously, since they have not received each other's SCI, the transmitting terminals Tx#1 and Tx#2 may select reserved resources whose time and frequency overlap. That is, the reserved resources of the transmitting terminals Tx#1 and Tx#2 may collide. Here, the description will continue on the assumption that a collision of the reserved resources of the transmitting terminals Tx#1 and Tx#2 has occurred.

[0056] After the transmitting terminals Tx#1 and Tx#2 each select reserved resources, they transmit an SCI including information specifying the reserved resources (steps S201, S202). This SCI is received by the terminal devices within the group including the cooperating terminal Co. When the cooperating terminal Co receives the SCI from the transmitting terminals Tx#1 and Tx#2, it determines whether or not the reserved resources of the transmitting terminals Tx#1 and Tx#2 collide (step S203). That is, the cooperating terminal Co determines whether or not the time and frequency of the reserved resources of the transmitting terminals Tx#1 and Tx#2 overlap. Here, it is determined that a collision of the reserved resources of the transmitting terminals Tx#1 and Tx#2 occurs.

[0057] Since a collision of the reserved resources occurs, the cooperating terminal Co calculates the error risk when the transmitting terminals Tx#1 and Tx#2 transmit data using the reserved resources (step S204). Specifically, the cooperating terminal Co calculates, as the error risk, the overlapping rate (Equation (1)) occupied by the overlapping region in the smaller of the reserved resources of the transmitting terminals Tx#1 and Tx#2, or calculates, as the error risk, the overlapping rate for each transmitting terminal (Equation (2)) occupied by the overlapping region in each of the reserved resources of the transmitting terminals Tx#1 and Tx#2. Note that the cooperating terminal Co may calculate the error risk by taking into account the information on the MCS applied to the data transmitted using the reserved resources, rather than using the overlapping rate as the error risk as it is.

[0058] When the calculated error risk of the coordination terminal Co is equal to or higher than a predetermined threshold, since there is a high possibility that errors will occur in the data transmitted by the transmission terminals #1 and #2 using the reserved resources, it is determined to cause one of the transmission terminals #1 and #2 to reselect resources. Here, it is assumed that it is determined to cause the transmission terminal Tx#1, which is the transmission terminal with the smaller reserved resources or the larger error risk when the error risk is equal to or higher than the predetermined threshold, to reselect resources.

[0059] When the coordination terminal Co determines to cause reselection of resources, it transmits a reselection request to the transmission terminal Tx#1 (step S205). The transmission terminal Tx#1 that receives this reselection request reselects a resource that does not overlap in time or frequency with the reserved resources of other terminal devices and is different from the reserved resources notified by the SCI in step S201 (step S206). Thereby, when the reserved resources initially selected by the transmission terminals Tx#1 and #2 collide and the error risk is high, the transmission terminal Tx#1 reselects resources and the collision of the reserved resources of the transmission terminals Tx#1 and #2 is avoided.

[0060] Specifically, for example, as shown in Fig. 6(a), consider the case where the transmission terminal Tx#2 notifies the reserved resource 303 by the SCI301 and the transmission terminal Tx#1 notifies the reserved resource 304 by the SCI302. In this case, when the coordination terminal Co receives the SCI301 and 302, it determines that the reserved resources 303 and 304 collide and calculates the error risk. In the example shown in Fig. 6(a), since the entire reserved resource 304 overlaps with the reserved resource 303 and the error risk is equal to or higher than the predetermined threshold, the coordination terminal Co transmits a resource reselection request to the transmission terminal Tx#1 corresponding to the reserved resource 304 before the timing of the reserved resources 303 and 304 arrives. Thereby, the transmission terminal Tx#1 reselects a resource 305 different from the reserved resource 304 and transmits data using the new reserved resource 305. In this way, when the error risk due to the colliding reserved resources is high, resource reselection is executed and the collision of the reserved resources is avoided.

[0061] On the one hand, for example, as shown in FIG. 6(b), consider the case where the transmitting terminal Tx#2 notifies the reserved resource 313 by SCI311 and the transmitting terminal Tx#1 notifies the reserved resource 314 by SCI312. In this case, when the cooperative terminal Co receives SCI311 and 312, it determines that the reserved resources 313 and 314 collide and calculates the error risk. In the example shown in FIG. 6(b), for both of the reserved resources 313 and 314, the ratio of the overlapping area is small and the error risk is less than a predetermined threshold value. Therefore, the cooperative terminal Co determines that re-selection of the resource is unnecessary. For this reason, the transmitting terminals Tx#1 and Tx#2 do not re-select the resource even if the reserved resources 313 and 314 collide, and transmit data using the reserved resources 313 and 314. For this reason, although a part of the data transmitted by the transmitting terminals Tx#1 and Tx#2 is transmitted in the overlapping area of the reserved resources 313 and 314, the ratio is small, so the possibility that each transmitted data is received erroneously is small. Also, since unnecessary re-selection of the reserved resources 313 and 314 does not occur, the possibility of re-collision of the resources due to re-selection can be reduced, and the communication efficiency can be improved.

[0062] As described above, according to the present embodiment, when the cooperative terminal determines that a collision of reserved resources of a plurality of transmitting terminals has occurred, the cooperative terminal calculates an error risk that an error occurs in the data due to the collision of the reserved resources, and requests re-selection of the resource when the error risk is equal to or greater than a predetermined threshold value. For this reason, when the error risk is low even if a collision of reserved resources occurs, re-selection of the resource by the transmitting terminal is not executed, unnecessary re-selection of the resource can be suppressed, and the possibility of re-collision of the reserved resources due to re-selection can be reduced. As a result, the communication efficiency in the wireless communication system can be improved.

[0063] (Embodiment 2) The feature of Embodiment 2 is that when a collision of reserved resources of a plurality of transmitting terminals occurs, the cooperative terminal determines whether to request re-selection of the resource to each transmitting terminal according to a predetermined rule.

[0064] Since the configuration of the wireless communication system according to Embodiment 2 is the same as that of Embodiment 1 (FIG. 1), the description thereof is omitted. Further, since the configuration of the transmission terminal 100 according to Embodiment 2 is the same as that of Embodiment 1 (FIG. 2), the description thereof is omitted.

[0065] FIG. 7 is a block diagram showing the configuration of the cooperative terminal 200 according to Embodiment 2. In FIG. 7, the same parts as those in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted. The cooperative terminal 200 shown in FIG. 7 has a request destination determination unit 401 and a reselection request generation unit 402 instead of the error risk calculation unit 223 and the reselection request generation unit 224 of the cooperative terminal 200 shown in FIG. 3.

[0066] When it is determined by the collision determination unit 222 that a collision of reserved resources has occurred, the request destination determination unit 401 determines the transmission terminal 100 of the request destination that requests reselection of resources. That is, the request destination determination unit 401 determines, among a plurality of transmission terminals 100 in which reserved resources collide, the transmission terminal 100 that requests reselection of resources and the transmission terminal 100 that does not request reselection of resources. Specifically, the request destination determination unit 401 determines the transmission terminal 100 of the request destination that requests reselection of resources according to any one or more of the following rules (A) to (E).

[0067] (A) Priority of data When the priority of data is specified by the SCI including information specifying the reserved resources, the request destination determination unit 401 determines the transmission terminal 100 that transmits data with a lower priority as the request destination for resource reselection. Collision and re-collision of reserved resources for transmitting data with a higher priority can be avoided.

[0068] (B) Reception timing of SCI The request destination determination unit 401 determines the transmission terminal 100 with an earlier or later reception timing of the SCI including information specifying the reserved resources as the request destination for resource reselection.

[0069] (C) Size of occupied area of reserved resources The request destination determination unit 401 determines the transmission terminal 100 with a small occupied area of reserved resources as the request destination for resource reselection. If the reserved resources have a small occupied area, the possibility of re - collision can be reduced even when re - selecting resources.

[0070] (D) Usage probability of reserved resources The request destination determination unit 401 determines the transmission terminal 100 with a low probability of actually using reserved resources for data transmission as the request destination for resource reselection. For example, in the case of initial - transmission data and re - transmission data, if the initial - transmission data is received normally, re - transmission is not executed, so re - transmission data may not actually be transmitted. Therefore, between the transmission terminal 100 that transmits initial - transmission data and the transmission terminal 100 that transmits re - transmission data, the transmission terminal 100 that transmits re - transmission data has a lower probability of actually using reserved resources. Also, the higher the number of re - transmission times of re - transmission data, the lower the probability of actually being transmitted. Thus, by causing the transmission terminal 100 that plans to transmit data with a large number of re - transmission times to re - select resources, the possibility of actual re - collision of reserved resources can be reduced.

[0071] (E) Transmission period of data The request destination determination unit 401 determines the transmission terminal 100 that transmits data transmitted aperiodically as the request destination for resource reselection. Between data transmitted periodically and data transmitted aperiodically, data transmitted periodically is more likely to have reserved resources specified for many terminal devices. This is because for data transmitted periodically, the reserved resources are also periodic. Therefore, by not changing the reserved resources for data transmitted periodically and changing the reserved resources for data transmitted aperiodically, collisions and re - collisions of reserved resources for data transmitted periodically can be avoided.

[0072] The request destination determination unit 401 determines whether or not a transmission terminal 100 that has reserved a resource reselects the resource by applying the above rules (A) to (E) alone or in combination. That is, the request destination determination unit 401 determines to cause any one of the transmission terminals 100 to reselect the resource according to the rule, and determines not to cause any other transmission terminal 100 to reselect the resource.

[0073] The reselection request generation unit 402 generates a reselection request for requesting the transmission terminal 100 determined as the request destination by the request destination determination unit 401 to reselect the resource.

[0074] Next, a communication control method by the cooperation terminal 200 configured as described above will be described with reference to the flowchart shown in FIG. 8. In FIG. 8, the same parts as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.

[0075] When the SCI including information for specifying each reserved resource is received from a plurality of transmission terminals 100 by the wireless communication unit 210 and the reception control unit 221 (step S101), the reserved resources of each transmission terminal 100 are notified to the collision determination unit 222. Then, the collision determination unit 222 determines whether or not a collision of the reserved resources occurs for each transmission terminal 100 (step S102). As a result of this determination, when no collision of the reserved resources occurs (step S102No), since it is not necessary to reselect the resource by the transmission terminal 100, the process ends.

[0076] On the other hand, when a collision of the reserved resources occurs (step S102Yes), the request destination determination unit 401 determines the transmission terminal 100 of the request destination that requests the reselection of the resource (step S301). Specifically, for example, by applying the rules shown in the above (A) to (E) alone or in combination, the transmission terminal 100 that reselects the resource is determined. At this time, for example, when the reserved resources of three or more transmission terminals 100 collide, two or more transmission terminals 100 may be determined as the transmission terminals 100 of the request destination according to the rules (A) to (E) above so as to resolve the collision of the reserved resources.

[0077] When the transmission terminal 100 of the request precedence is determined, a reselection request for requesting resource reselection is generated by the reselection request generation unit 402, and is transmitted to the transmission terminal 100 of the request destination by the transmission control unit 227 and the wireless communication unit 210 (step S105).

[0078] As described above, when a collision occurs in the reserved resources of a plurality of transmission terminals 100, the cooperating terminal 200 determines the transmission terminal 100 of the request destination that requests resource reselection, thereby determining whether or not the transmission terminal 100 performs resource reselection, and transmits a resource reselection request to the transmission terminal 100 of the request destination. As a result, even when a plurality of cooperating terminals 200 request resource reselection to the transmission terminal 100, a common transmission terminal 100 is requested to perform reselection, suppressing unnecessary reselection of resources and reducing the possibility of re-collision of reserved resources due to reselection. As a result, the communication efficiency in the wireless communication system can be improved.

[0079] As described above, according to the present embodiment, when the cooperating terminal determines that a collision has occurred in the reserved resources of a plurality of transmission terminals, the cooperating terminal determines the transmission terminal of the request destination that requests resource reselection according to a rule, and requests the determined transmission terminal of the request destination to perform resource reselection. Therefore, even when a plurality of cooperating terminals request resource reselection, a common transmission terminal is requested to perform reselection, unnecessary reselection of resources can be suppressed, and the possibility of re-collision of reserved resources due to reselection can be reduced. As a result, the communication efficiency in the wireless communication system can be improved.

[0080] Note that the above-described embodiments can be implemented in appropriate combinations. That is, for example, the error risk may be calculated as in Embodiment 1 to determine whether or not resource reselection is performed, and the request destination for resource reselection may be determined as in Embodiment 2.

Explanation of Reference Numerals

[0081] 110 and 220 Processors 111 and 221 Reception Control Units 112 Resource Selection Unit 113 and 225 Transmission Data Generation Units 114 and 226 Control Information Generation Units 115 and 227 Transmission Control Units 120 and 230 Memories 130 and 210 Wireless Communication Units 222 Collision Determination Unit 223 Error Risk Calculation Unit 224 and 402 Re-selection Request Generation Units 401 Request Destination Determination Unit

Claims

1. A wireless communication unit that wirelessly communicates with a plurality of transmission terminals, and a processor connected to the wireless communication unit, wherein the processor determines whether a collision of wireless resources reserved for use by the plurality of transmission terminals in data transmission occurs, and when it is determined that a collision of the wireless resources occurs, causes the wireless communication unit to transmit information requesting re-selection of the wireless resources including executing a process, wherein the process includes a process of determining a first transmission terminal that transmits the information from the plurality of transmission terminals, and a process of determining a second transmission terminal that does not transmit the information from the plurality of transmission terminals, wherein the first transmission terminal is determined according to a rule based on the priority of data transmitted using the reserved wireless resources, the reception timing of control information notifying the reserved wireless resources, and the occupied area of the reserved wireless resources, A wireless communication device characterized by the above.

2. The processor calculates an error risk indicating the possibility that data is incorrect when data is transmitted using the colliding wireless resources, and determines to transmit the information when the calculated error risk is equal to or greater than a predetermined threshold value The wireless communication device according to claim 1, characterized by including the process.

3. The processor calculates the error risk based on the ratio of the area overlapping with the wireless resources reserved by other transmission terminals in the occupied area of the wireless resources reserved by each transmission terminal The wireless communication device according to claim 2, characterized by the above.

4. The processor Calculating the error risk based on the MCS (Modulation and Coding Scheme) of data transmitted using the radio resources reserved by each transmitting terminal The wireless communication device according to claim 3, characterized in that

5. For the transmitting terminal that has received the information determined by the processor to be transmitted, Based on at least one of the priority of data transmitted using the reserved radio resources, the reception timing of control information for notifying the reserved radio resources, the occupied area of the reserved radio resources, and the transmission period of data transmitted using the reserved radio resources, reselect the radio resources The wireless communication device according to claim 1, characterized in that

6. The wireless communication unit Transmits information requesting re-selection of the radio resources using a feedback channel for transmitting feedback information The wireless communication device according to claim 1, characterized in that

7. The information is information for causing the transmitting terminal that has received the information among the plurality of transmitting terminals to reselect radio resources The wireless communication device according to claim 1, characterized in that

8. A transmitting terminal among a plurality of transmitting terminals that perform wireless communication with a wireless communication device, A transmitting unit that transmits information indicating a first radio resource reserved for data transmission to the wireless communication device A first transmitting terminal that detects a collision between a second radio resource reserved by another transmitting terminal among the plurality of transmitting terminals and the first radio resource, and transmits information requesting reselection of a radio resource from the plurality of transmitting terminals according to rules based on the priority of data transmitted using the reserved radio resource, the reception timing of control information for notifying the reserved radio resource, and the occupied area of the reserved radio resource; when determining a second transmitting terminal that does not transmit information requesting reselection of the radio resource, a receiving unit that receives the information requesting reselection of the radio resource from the radio communication device, A control unit that selects a third radio resource different from the first radio resource in response to receiving the information requesting reselection of the radio resource, A transmitting terminal characterized by comprising the above.

9. A wireless communication system having a first terminal device, a second terminal device, and a third terminal device, The first terminal device and the second terminal device have, A transmitting unit that transmits control information for specifying a radio resource reserved for data transmission, The third terminal device has, A wireless communication unit that wirelessly communicates with the first terminal device and the second terminal device, A processor connected to the wireless communication unit, The processor, Determines whether a collision occurs in the radio resources reserved by the first terminal device and the second terminal device based on the control information received by the wireless communication unit, When it is determined that a collision of the radio resources occurs, includes executing a process of causing information requesting reselection of the radio resources to be transmitted, The process includes, A process of determining a first transmitting terminal that transmits the information from the first terminal device and the second terminal device, A process of determining a second transmitting terminal that does not transmit the information from the first terminal device and the second terminal device. The first transmitting terminal is determined according to rules based on the priority of data transmitted using reserved radio resources, the reception timing of control information for notifying the reserved radio resources, and the occupied area of the reserved radio resources. A wireless communication system characterized by the above.

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